A variety of carbon blacks are known in the art. These carbon blacks primarily differ in properties from each other and are made by different procedures. The use of the carbon black depends upon its properties. Since the carbon black as such cannot be sufficiently characterized by its chemical composition or by its ingredients, it has become widely accepted to characterize the carbon black by the properties it exhibits. Thus, the carbon black can, for e.g., be characterized by its surface area, which is usually an inverse measurement of the primary particle size. Another important characteristic of the carbon black is its structure, which is a measure of the complexity of the individual carbon black aggregates or of the number of primary particles “fused” together in one carbon black aggregate.
One common application of the carbon black is as a performance enhancing filler in rubber and other polymers. The reinforcing action of the carbon black depends on the interaction, both chemical and physical, between the carbon black and the polymeric matrix. This interaction also governs the performance of the filled rubber/polymer and its applications in several aspects. Efforts have been made to correlate properties of the rubber incorporating the carbon black and properties of the carbon black. There is not found any single property of carbon black that, if made high or low enough, results in an ideal rubber composition. Where certain properties of the carbon black are related to abrasion resistance of the rubber, others are related to the tensile strength or heat build-up.
It is found that high abrasion resistance of a carbon black/rubber composition is one desirable property of such composition. Another desirable property is low heat build-up or low hysteresis. The heat build-up is a measurement of how much of the elastic deformation energy put into a product made of carbon black/rubber compound remains in the compound as heat after the deformation forces have been released. The hysteresis or heat build-up is measured by measuring the temperature of a sample subjected to deformations. This property is extremely crucial when making tires with such carbon black/rubber composition. The higher the heat build-up, the greater the energy loss of the vehicle using the tyres (hence, lower the fuel efficiency); also, chances are that tires made from such rubbers are destroyed sooner. It is, therefore, very desirable to reduce the heat build-up of rubber compositions by providing low hysteresis carbon black. Several attempts have been made in the past to provide processes for producing low hysteresis carbon blacks. Some of these processes are cited below.
U.S. Pat. No. 4,988,493 discloses a process and apparatus for producing carbon blacks which give low hysteresis and good wear when used in rubber compounds for reinforcement, particularly in rubber tires. The process comprises supplying a linear, substantially non-swirling flow of the combustion gases into a feedstock oil injection zone in a reactor, supplying at least two independently controlled streams of carbon black feedstock oil into separate segments of the flow of the combustion gases in the feedstock oil injection zone, wherein separate carbon black forming reactions are respectively effected in separate segments of the flow of combustion gases, and immediately thereafter supplying the combustion gas segments in which said separate carbon black forming reactions have been effected into an aggregate-forming zone whereby a carbon black product is produced which, when compounded in rubber compositions, provides said rubber compositions with improved hysteresis loss and treadwear resistance properties.
U.S. Pat. No. 4,327,069 discloses a process for producing carbon black of negative tint residual by pyrolytic decomposition of hydrocarbons in a carbon black furnace. The process comprises producing a first carbon black forming mixture in a first carbon black forming zone which is a high structure zone, passing the first carbon black forming mixture from the first carbon black forming zone to a second carbon black forming zone which is a low structure zone to produce a second carbon black forming mixture, passing the second carbon black forming mixture into a quench zone where the second carbon black forming mixture is contacted with a quench fluid to produce a carbon black containing smoke at a temperature below carbon black formation temperature, and separating carbon black of negative tint residual from the smoke.
The known processes of the prior art require complex process control to obtain carbon black with low hysteresis. There is, therefore, felt a need for a simple process for producing carbon black in-which the surface chemistry of the carbon black is conveniently altered during the manufacturing process to produce carbon black, which, when combined with rubber compositions decreases the hysteresis and thus lowers the heat build-up in the rubber composition to thereby provide high-performance tires.